Managing ewe nutrition is the most important factor to ensure best reproductive performance. Use the Condition scoring tool to help ensure ewes meet production targets and enable timely decisions to optimise reproduction rates. The condition score (CS) of the ewes is the most important determinant of ovulation rate.
The target condition score at joining is a balance between reproductive performance, stocking rate and the cost of achieving that score. In Merinos, the reproductive rate response to condition score is linear between CS 1.5 to 4.5. At CS 4 or higher during lambing the risk of dystocia increases.
When managing breeding flocks consider the following strategies:
- Join maiden ewes and adults separately as they have different ram requirements.
- Ewe health is extremely important. Any health issue, such as worm burdens, liver fluke or footrot will slow weight gain or cause weight loss resulting in lower reproductive rates.
- Avoid joining ewes within two weeks of shearing as shearing can disrupt cycling activity.
- Avoid joining ewes with full wool as joining can be physically more difficult.
- Avoid joining ewes on pastures that may be toxic to sheep. For example, high endophyte perennial ryegrass pastures can lower conception rates and lambing performance by as much as 20%, even without visible ryegrass staggers.
- Avoid severe stress when joining ewes as embryo loss may be higher. For example, more than 1 kg liveweight loss per week or extreme variation in feed quality will cause stress.
Joining maiden ewes
Bodyweight is the critical factor with maiden ewes. Condition score ewes as they near mature weight to ensure successful joining and increase the percentage of lambs weaned to ewes joined.
Maiden Merino ewes should weigh at least 75–80% of their adult weight before joining. Use the Standard reference weight tool and the Successful joining tool to understand the minimum target liveweight for maiden ewes before joining.
Crossbred and shedder ewe lambs and some Merino bloodlines can be successfully joined at 7-10 months if adequate feed can be provided until time of lambing. Liveweight at joining is critical – ensure ewe lambs reach a minimum of 45 kg to achieve optimal performance. For each additional kilogram between 35-45 kg at joining, weaning rate increases by around 3%. Ensure ewe lambs have access to high-quality feed during pregnancy to enable them to maintain condition score 3 or better at lambing.